Radiosensitivity Of Lung Cancer Cells Research Articles

Mechanism of Musashi2 affecting radiosensitivity of lung cancer by modulating DNA damage repair.

Identifying new targets for overcoming radioresistance is crucial for improving the efficacy of lung cancer radiotherapy, given that tumor cell resistance is a leading cause of treatment failure. Recent research has spotlighted the significance of Musashi2 (MSI2) in cancer biology. In this study, we first demonstrated that MSI2 plays a key function in regulating the radiosensitivity of lung cancer. The expression of MSI2 is negatively correlated with overall survival in cancer patients, and the knockdown of MSI2 inhibits tumorigenesis and increases radiosensitivity of lung cancer cells. Cellular radiosensitivity, which is closely linked to DNA damage, is influenced by MSI2 interaction with ataxia telangiectasia mutated and Rad3-related kinase (ATR) and checkpoint kinase 1 (CHK1) post-irradiation; moreover, knockdown of MSI2 inhibits the ATR-mediated DNA damage response pathway. RNA-binding motif protein 17 (RBM17), which is implicated in DNA damage repair, exhibits increased interaction with MSI2 post-irradiation. We found that knockdown of RBM17 disrupted the interaction between MSI2 and ATR post-irradiation and increased the radiosensitivity of lung cancer cells. Furthermore, we revealed the potential mechanism of MSI2 recruitment into the nucleus with the assistance of RBM17 to activate ATR to promote radioresistance. This study provides novel insights into the potential application of MSI2 as a new target in lung cancer radiotherapy.

Targeting FBXO22 enhances radiosensitivity in non-small cell lung cancer by inhibiting the FOXM1/Rad51 axis

Radioresistance is a major constraint on the efficacy of lung cancer radiotherapy, but its mechanism has not been fully elucidated. Here, we found that FBXO22 was aberrantly highly expressed in lung cancer and that FBXO22 knockdown increased the radiosensitivity of lung cancer cells. Mechanistically, FBXO22 promoted Rad51 gene transcription by increasing the level of FOXM1 at the Rad51 promoter, thereby inducing the formation of lung cancer radioresistance. Furthermore, we found that deguelin, a potential inhibitor of FBXO22, enhanced radiosensitivity in an FBXO22/Rad51-dependent manner and was safely tolerated in vivo. Collectively, our results illustrate that FBXO22 induces lung cancer radioresistance by activating the FOXM1/Rad51 axis and provide preclinical evidence for the clinical translation of this critical target.

The kinesin light chain-2, a target of mRNA stabilizing protein HuR, inhibits p53 protein phosphorylation to promote radioresistance in NSCLC.

Radioresistance hinders radiotherapy for the treatment of lung cancer. Kinesin light chain-2 (KLC2) has been found to be upregulated in lung cancer and also to be associated with poor prognosis. This study aimed to investigate the effect of KLC2 on radiosensitivity in lung cancer. The radioresistant role of KLC2 was determined by colony formation, neutral comet assay, and γH2AX immunofluorescent staining assay. We further verified the function of KLC2 in a xenograft tumor model. The downstream of KLC2 was identified through gene set enrichment analysis and validated by western blot. Finally, we analyzed clinical data from the TCGA database to reveal the upstream transcription factor of KLC2, which was validated by RNA binding protein immunoprecipitation assay. Here, we found that downregulation of KLC2 could significantly reduce colony formation, increase γH2AX level, and double-stranded DNA breaks in vitro. Meanwhile, overexpressed KLC2 significantly increased the proportion of the S phase in lung cancer cells. KLC2 knockdown could activate P53 pathway, and ultimately promoting radiosensitivity. The mRNA of KLC2 was observed to bind with Hu-antigen R (HuR). The mRNA and protein expression of KLC2 in lung cancer cells was significantly reduced when combined with siRNA-HuR. Interestingly, KLC2 overexpression significantly increased the expression of HuR in lung cancer cells. Taken together, these results indicated that HuR-KLC2 forms a positive feedback loop, which decreases the phosphorylation of p53 and thereby weaken the radiosensitivity of lung cancer cells. Our findings highlight the potential prognosis and therapeutic target value of KLC2 in lung cancer patients treated with radiotherapy.

Ginsenoside Rg3 enhances the radiosensitivity of lung cancer A549 and H1299 cells via the PI3K/AKT signaling pathway.

Lung cancer is one of the most common cancers and the leading cause of cancer-related deaths in the world. Radiation is widely used for the treatment of lung cancer. However, radioresistance and toxicity limit its effectiveness. Ginsenoside Rg3 (Rg3) is a positive monomer extracted from ginseng and has been shown to the anti-cancer ability on many tumors. The aim of the present study was to ascertain whether Rg3 is able to enhance the radiosensitivity of lung cancer cells and investigate the underlying mechanisms. The effect of Rg3 on cell proliferation was examined by Cell Counting Kit-8 (CCK-8) and radiosensitivity was measured by colony formation assay. Flow cytometry, transwell, and wound healing assay were used to determine apoptosis, cell cycle, and metastasis. Western blot was used to detect the main protein levels of the PI3K/AKT signaling pathway. We found that Rg3 inhibited cell proliferation, promoted apoptosis, and suppressed migration and invasion in radio-induced lung cancer cells. In addition, Rg3 increased the proportion of G2/M phase cells and inhibited the formation of cell colonies. Moreover, Rg3 decreased the expression levels of PI3K, p-AKT, and PDK1 in radio-induced cells. These findings indicate that Rg3 may be able to enhance the radiosensitivity in lung cancer cells by the PI3K/AKT signaling pathway. These results demonstrate the therapeutic potential of Rg3 as a radiosensitizer for lung cancer.

ATAD2 suppression enhances the combinatorial effect of gemcitabine and radiation in pancreatic cancer cells

Amalgamation of target-based approach along with chemo and/or radiotherapy could be an effective strategy to combat pancreatic cancer (PC). ATAD2 (ATPase family AAA domain containing 2) is a potential oncoprotein and a poor prognostic factor in PC. ATAD2 inhibition sensitizes pancreatic cancer cells (PCCs) to gemcitabine (GEM). ATAD2 silencing also enhances radio-sensitivity in lung cancer cells. We therefore hypothesise that ATAD2 suppression along with application of GEM and radiation could show additive/synergistic response in reducing PC progression. At first, immunofluorescence and western blot analysis are carried out to investigate ATAD2 expression upon irradiation in PCCs (BxPC3, and PANC1). Colony forming assay is performed to analyse the radio-sensitization effect of ATAD2 suppressed PCCs in absence and presence of GEM. To evaluate the consequences of irradiation, expression of markers for DNA damage and repair as well as apoptosis and autophagy are also assessed. Results indicate that ATAD2 is elevated in irradiated PCCs. Silencing ATAD2 sensitizes PCCs to radiation. Survival fraction analysis of PCCs shows that combination treatment of GEM and radiation (with minimal doses) is more effective when ATAD2 is suppressed. Further, when GEM-radiation combination is applied to ATAD2 silenced PCCs, expression of DNA damage marker like γH2AX is induced, whereas DNA damage repair proteins (pChk1, and pChk2) are downregulated. Moreover, ATAD2 suppressed PCCs are more susceptible to apoptosis and autophagy in presence of radiation and GEM. Collectively, these findings support our hypothesis and demonstrate that targeting ATAD2 enhances efficacy of GEM-radiation treatment in PCCs.

Triptolide increases the radiosensitivity of lung cancer cells by inhibiting DNA repair and inducing apoptosis

Objective: To investigate the effect of triptolide on radiosensitivity of lung cancer cells and its mechanism. Methods: The lung cancer cells H1299, A549, H157 and H838 were cultured. The strongest radio resistance cell line, H1299 was selected by cell clone formation experiment and for the subsequent experiments. 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H tetrazolium bromide (MTT) was used to detect the effect of different concentrations of triptolide on the proliferation of H1299 cells. The optimal concentration of triptolide was 50nmol/L, and the optimal treatment time was 48 hours. The H1299 cells were divided into the control group, triptolide group (50 nmol/L), 4 Gy group and triptolide+ 4 Gy group. Flow cytometry was used to detect the apoptosis rate of H1299 cell. Western Blot was used to detect the proteins expression levels of p-Chk2, p-ATM, p-p53, Bcl-2, Bax and cleaved-Caspase 3. Results: The apoptotic rate and protein levels of Bax, cleaved-Caspase 3, p-Chk2, p-ATM and p-p53 in the 4 Gy group were (12.38±1.34)%, 0.42±0.04, 0.38±0.04, 0.98±0.11, 0.73±0.08, 0.95±0.09, respectively, higher than (3.26±2.43)%, 0.22±0.02, 0.23±0.03, 0.32±0.03, 0.21±0.02, 0.25±0.03 in the control group (P<0.05). However, the protein level of Bcl-2 was (0.52±0.05), lower than (0.93±0.09) of the control group (P<0.05). The survival fraction (0.462) and protein level of Bcl-2 (0.44±0.04) in the triptolide group were lower than those of the control group (0.702 and 0.93±0.09, P<0.05). The apoptotic rate and the protein levels of Bax and cleaved-Caspase 3 in the triptolide group were (9.27±1.08)%, 0.45±0.05, 0.41±0.04, respectively, higher than (3.26±2.43)%, 0.22±0.02, 0.23±0.03 in the control group (P<0.05), and the sensitization ratio in the triptolide group was 1.579. The apoptosis rate, Bax and cleaved Caspase 3 protein expression levels in triptolide + 4 Gy group were (26.53±2.19)%, 0.91±0.09 and 0.79±0.08, respectively, higher than (12.38±1.34)%, 0.42±0.04 and 0.38±0.04 in 4 Gy group (P<0.05). The expression level of Bcl-2 protein was (0.21±0.02), lower than (0.52±0.05) in 4 Gy group (P<0.05). Conclusion: Triptolide increases the radiosensitivity of radiation-induced lung cancer cells by inhibiting DNA repair and inducing apoptosis.

Hemin enhances radiosensitivity of lung cancer cells through ferroptosis

The principle underlying radiotherapy is to kill cancer cells while minimizing the harmful effects on non-cancer cells, which has still remained as a major challenge. In relation, ferroptosis has recently been proposed as a novel mechanism of radiation-induced cell death. In this study, we investigated and demonstrated the role of Hemin as an iron overloading agent in the generation of reactive oxygen species (ROS) induced by ionizing radiation in lung cancer and non-cancer cells. It was found that the presence of Hemin in irradiated lung cancer cells enhanced the productivity of initial ROS, resulting in lipid peroxidation and subsequent ferroptosis. We observed that application of Hemin as a co-treatment increased the activity of GPx4 degradation in both cancer and normal lung cells. Furthermore, Hemin protected normal lung cells against radiation-induced cell death, in that it suppressed ROS after radiation, and boosted the production of bilirubin which was a lipophilic ROS antioxidant. In addition, we demonstrated significant FTH1 expression in normal lung cells when compared to lung cancer cells, which prevented iron from playing a role in increasing IR-induced cell death. Our findings demonstrated that Hemin had a dual function in enhancing the radiosensitivity of ferroptosis in lung cancer cells while promoting cell survival in normal lung cells.

The Role and Mechanism of ATM-Mediated Autophagy in the Transition From Hyper-Radiosensitivity to Induced Radioresistance in Lung Cancer Under Low-Dose Radiation.

Objective: This study aimed to investigate the effect of ataxia telangiectasia mutated (ATM)–mediated autophagy on the radiosensitivity of lung cancer cells under low-dose radiation and to further investigate the role of ATM and its specific mechanism in the transition from hyper-radiosensitivity (HRS) to induced radioresistance (IRR).Methods: The changes in the HRS/IRR phenomenon in A549 and H460 cells were verified by colony formation assay. Changes to ATM phosphorylation and cell autophagy in A549 and H460 cells under different low doses of radiation were examined by western blot, polymerase chain reaction (PCR), and electron microscopy. ATM expression was knocked down by short interfering RNA (siRNA) transfection, and ATM-regulated molecules related to autophagy pathways were screened by transcriptome sequencing analysis. The detection results were verified by PCR and western blot. The differential metabolites were screened by transcriptome sequencing and verified by colony formation assay and western blot. The nude mouse xenograft model was used to verify the results of the cell experiments.Results: (1) A549 cells with high expression of ATM showed positive HRS/IRR, whereas H460 cells with low expression of ATM showed negative HRS/IRR. After the expression of ATM decreased, the HRS phenomenon in A549 cells increased, and the radiosensitivity of H460 cells also increased. This phenomenon was associated with the increase in the autophagy-related molecules phosphorylated c-Jun N-terminal kinase (p-JNK) and autophagy/Beclin 1 regulator 1 (AMBRA1). (2) DL-Norvaline, a product of carbon metabolism in cells, inhibited autophagy in A549 cells under low-dose radiation. DL-Norvaline increased the expression levels of ATM, JNK, and AMBRA1 in A549 cells. (3) Mouse experiments confirmed the regulatory role of ATM in autophagy and metabolism and its function in HRS/IRR.Conclusion: ATM may influence autophagy through p-JNK and AMBRA1 to participate in the regulation of the HRS/IRR phenomenon. Autophagy interacts with the cellular carbon metabolite DL-Norvaline to participate in regulating the low-dose radiosensitivity of cells.

MicroRNA-499 serves as a sensitizer for lung cancer cells to radiotherapy by inhibition of CK2α-mediated phosphorylation of p65

The present study aimed to define the tumor-suppressive role of microRNA-499 (miR-499) in lung cancer cells and its underlying mechanism. First, qRT-PCR analysis revealed poor expression of miR-499 in clinical samples and cell lines of lung cancer. Next, we performed loss- and gain-of-function experiments for the expression of miR-499 in lung cancer cells exposed to irradiation (IR) to determine the effect of miR-499 expression on cell viability and apoptosis as well as tumor growth. Results showed that overexpression of miR-499 inhibited cell viability, enhanced the radiosensitivity of lung cancer cells, and promoted cell apoptosis under IR. Furthermore, CK2α was verified to be a target of miR-499, and miR-499 was identified to repress p65 phosphorylation by downregulating CK2α expression, which ultimately diminished the survival rate of lung cancer cells under IR. Collectively, the key findings of the study illustrate the tumor-inhibiting function of miR-499 and confirmed that miR-499-mediated CK2α inhibition and altered p65 phosphorylation enhances the sensitivity of lung cancer cells to IR.

Capilliposide C from Lysimachia capillipes Restores Radiosensitivity in Ionizing Radiation-Resistant Lung Cancer Cells Through Regulation of ERRFI1/EGFR/STAT3 Signaling Pathway.

AimsRadiation therapy is used as the primary treatment for lung cancer. Unfortunately, radiation resistance remains to be the major clinic problem for lung cancer patients. Lysimachia capillipes capilliposide C (LC-C), an extract from LC Hemsl, has demonstrated multiple anti-cancer effects in several types of cancer. Here, we investigated the potential therapeutic impacts of LC-C on radiosensitivity in lung cancer cells and their underlying mechanisms.MethodsNon-small cell lung cancer cell lines were initially irradiated to generate ionizing radiation (IR)-resistant lung cancer cell lines. RNA-seq analysis was used to examine the whole-transcriptome alteration in IR-resistant lung cancer cells treated with or without LC-C, and the differentially expressed genes with most significance were verified by RT-qPCR. Colony formation assays were performed to determine the effect of LC-C and the target gene ErbB receptor feedback inhibitor 1 (ERRFI1) on radiosensitivity of IR-resistant lung cancer cells. In addition, effects of ERRFI1 on cell cycle distribution, DNA damage repair activity were assessed by flow cytometry and γ-H2AX immunofluorescence staining respectively. Western blotting was performed to identify the activation of related signaling pathways. Tumor xenograft experiments were conducted to observe the effect of LC-C and ERRFI1 on radiosensitivity of IR-resistant lung cancer cells in vivo.ResultsCompared with parental cells, IR-resistant lung cancer cells were more resistant to radiation. LC-C significantly enhanced the effect of radiation in IR-resistant lung cancer cells both in vitro and in vivo and validated ERRFI1 as a candidate downstream gene by RNA-seq. Forced expression of ERRFI1 alone could significantly increase the radiosensitivity of IR-resistant lung cancer cells, while silencing of ERRFI1 attenuated the radiosensitizing function of LC-C. Accordingly, LC-C and ERRFI1 effectively inhibited IR-induced DNA damage repair, and ERRFI1 significantly induced G2/M checkpoint arrest. Additional investigations revealed that down-regulation of EGFR/STAT3 pathway played an important role in radiosensitization between ERRFI1 and LC-C. Furthermore, the high expression level of ERRFI1 was associated with high overall survival rates in lung cancer patients.ConclusionsTreatment of LC-C may serve as a promising therapeutic strategy to overcome the radiation resistance and ERRFI1 may be a potential therapeutic target in NSCLC.

Maf1 suppression of ATF5-dependent mitochondrial unfolded protein response contributes to rapamycin-induced radio-sensitivity in lung cancer cell line A549.

mTOR is well known to promote tumor growth but its roles in enhancing chemotherapy and radiotherapy have not been well studied. mTOR inhibition by rapamycin can sensitize cancer cells to radiotherapy. Here we show that Maf1 is required for rapamycin to increase radio-sensitivity in A549 lung cancer cells. In response to ionizing radiation (IR), Maf1 is inhibited by Akt-dependent re-phosphorylation, which activates mitochondrial unfolded protein response (UPRmt) through ATF5. Rapamycin suppresses IR-induced Maf1 re-phosphorylation and UPRmt activation in A549 cells, resulting in increased sensitivity to IR-mediated cytotoxicity. Consistently, Maf1 knockdown activates ATF5-transcription of mtHSP70 and HSP60, enhances mitochondrial membrane potential, reduces intracellular ROS levels and dampens rapamycin’s effect on increasing IR-mediated cytotoxicity. In addition, Maf1 overexpression suppresses ethidium bromide-induced UPRmt and enhances IR-mediated cytotoxicity. Supporting our cell-based studies, elevated expression of UPRmt makers (mtHSP70 and HSP60) are associated with poor prognosis in patients with lung adenocarcinoma (LAUD). Together, our study reveals a novel role of Maf1-UPRmt axis in mediating rapamycin’s enhancing effect on IR sensitivity in A549 lung cancer cells.

Suberoylanilide hydroxamic acid enhances the radiosensitivity of lung cancer cells through acetylated wild-type and mutant p53-dependent modulation of mitochondrial apoptosis.

ObjectiveSuberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, has shown potential as a candidate radiosensitizer for many types of cancers. This study aimed to explore the radiosensitization mechanism of SAHA in lung cancer cells.MethodsMutations in p53 were generated by site-directed mutagenesis using polymerase chain reaction. Transfection was performed to generate H1299 cells carrying wild-type or mutant p53. The radiosensitizing enhancement ratio was determined by clonogenic assays. Mitochondrial apoptosis was detected using JC-1 staining and flow cytometry analysis.ResultsOur results showed that SAHA induced radiosensitization in H1299 cells expressing wild-type p53, p53R175H or p53P223L, but this enhanced clonogenic cell death was not observed in parental H1299 (p53-null) cells or H1299 cells expressing p53 with K120R, A161T and V274R mutations. In SAHA-sensitized cells, mitochondrial apoptosis was induced following exposure to irradiation. Additionally, we observed that a secondary mutation at K120 (K120R) could eliminate p53-mediated radiosensitization and mitochondrial apoptosis.ConclusionsThe results of this study suggest that wild-type and specific mutant forms of p53 mediate SAHA-induced radiosensitization by regulating mitochondrial apoptosis, and the stabilization of K120 acetylation by SAHA is the molecular basis contributing to radiosensitization in lung cancer cells.

Radio-sensitizing effects of microRNA-27a elevation in lung cancer cells by inhibiting ZEB1 expression and activating DNA damage repair pathway.

MicroRNAs (miRNAs or miRs) exert either as tumor-inhibiting or oncogenic roles in tumorigenesis of lung cancer. In the present study, we identified a novel microRNA (miR)-27a as being involved in the radiosensitivity of lung cancer cells. Therefore, we sought to characterize its potential underlying mechanism in lung cancer cell sensitivity to radiotherapy. To this end, A549 and H460 cells irradiated with 8 Gy irradiation (IR) were used as a cell model. RT-qPCR exhibited that the expression of miR-27a increased, whereas ZEB1 was poorly expressed in A549 and H460 cells exposed to IR. As reflected by dual-luciferase reporter gene assay, miR-27a could target and inversely modulate ZEB1 expression. Gain- and loss-of-function experiments exhibited that miR-27 inhibition promoted proliferation of IR-treated A549 and H460 cells and reduced the sensitivity of A549 and H460 cells to radiotherapy, which was rescued by silencing of ZEB1. Further, miR-27a inhibition disrupted the homologous recombination (HR)-mediated DNA repair, evidenced by reduced ATM, pCHK2 and Rad51 levels. Collectively, miR-27a activates HR-mediated DNA repair by inhibiting ZEB1 expression to enhance the radiosensitivity of lung cancer cells, highlighting a therapeutic target for lung cancer radiosensitivity.

Effect of LncRNA UCA1 on radiosensitivity of lung cancer cells and its mechanism

Objective To evaluate the effect of long-chain non-coding RNA (LncRNA) UCA1 on the proliferation, apoptosis and radiosensitivity of lung cancer cell and to explore the underlying mechanism. Methods qRT-PCR was used to detect the expression of UCA1 and miR-513a-5p in lung cancer cell A549, H1299 and normal human lung cell HBE. The si-con group (transfected si-con), si-UCA1 group (transfected si-UCA1), miR-513a-5p group (transfected miR-513a-5p mimics), miR-NC group (transfected miR-NC), IR+ si-con group (transfected si-con, and irradiated), IR+ si-UCA1 group (transfected miR-NC and irradiated), IR+ miR-513a-5p group (transfected miR-513a-5p mimics and irradiated), IR+ miR-NC group (transfected miR-NC and irradiated), IR+ si-UCA1+ anti-miR-513a-5p group (co-transfected si-UCA1, anti-miR-513a-5p and irradiated) were transfected into the A549 and H1299 cells by liposome method, and then the cells in certain groups were subject to 4Gy irradiation. The cell proliferation of each group was detected by MTT assay. The sensitivity enhancement ratio was assessed by clone formation assay. The cell apoptosis of each group was detected by flow cytometry. The fluorescence activity of each group was detected by dual-fluorescein gene detection assay. Results Compared with human normal lung cell HBE, the expression levels of UCA1 were significantly up-regulated in the lung cancer cell A549 and H1299(both P<0.05), whereas those of miR-513a-5p were significantly down-regulated (both P<0.05). Inhibition of UCA1 and overexpression of miR-513a-5p significantly inhibited cell proliferation, promoted cell apoptosis and increased the sensitivity of radiation exposure of A549 and H1299(sensitivity enhancement ratio=1.897, 2.146 and 1.615, 1.872). miR-513a-5p could suppress the fluorescence activity of wild-type UCA1 cells, and UCA1 could negatively regulate the expression of miR-513a-5p. Inhibition of miR-513a-5p could reverse the enhancement effect of inhibiting UCA1 upon the radiosensitivity of lung cancer cells. Conclusions Inhibition of LncRNA UCA1 can enhance the sensitivity of radiation exposure to lung cancer cells. The mechanism may be related to the targeted inhibition of miR-513a-5p. Key words: UCA1 gene; miR-513a-5p gene; Radiosensitivity; Lung cancer cell line

The role and mechanisms of zinc oxide nanoparticles in the improvement of the radiosensitivity of lung cancer cells in clinically relevant megavoltage radiation energies in-vitro

Objective(s): Semiconductor zinc oxide nanoparticles (ZnO NPs) have unique properties, such as inherent selectivity and photosensitization effects under ultraviolet (UV) radiation. ZnO NPs serve as promising anticancer agents. However, UV radiation limits their penetration into the body. In most clinical settings, it is essential to use high-energy photons in the treatment of deep-seated tumors. The present study aimed to evaluate the radiosensitization effects of ZnO NPs on human lung cancer cells under megavoltage (MV) X-ray irradiation. Materials and Methods: ZnO NPs with the mean diameter of seven nanometers were synthesized and characterized. The cytotoxicity and cellular uptake of ZnO NPs were evaluated in SKLC-6 lung cancer and MRC-5 normal lung cells using the 3-(4,5-dimethylthiazol-yl)-5(3-carboxymethoxyphenyl)-2H-tetrazolium (MTT) and inductively coupled plasma-mass spectrometry assays, respectively. In addition, the radiosensitization effects of ZnO NPs were investigated under MV irradiation using a clonogenic survival assay. Apoptosis induction and DNA damage were also evaluated using flow cytometry and cytokinesis-block micronucleus assay, respectively.Results: ZnO NPs were taken up and reduced the viability of the cancer cells at a higher rate compared to the normal cells. Moreover, ZnO NPs significantly enhanced the radiosensitivity of the cancer cells with the sensitizer enhancement ratios of 1.23 and 1.31 at the concentrations of 10 and 20 μg/ml, respectively. However, they had no significant effect on the radiosensitivity of the normal cells. Apoptosis induction and DNA damage also improved at a higher rate in the cancer cells compared to the normal cells with the combination of ZnO NPs with MV radiation.Conclusion: According to the results, ZnO NPs had the potential to be a selective radiosensitizer for lung cancer radiotherapy under MV X-ray irradiation. Some of the cytotoxic and genotoxic mechanisms in radiosensitization by ZnO NPs were elevated apoptosis induction and DNA damage levels.

Silencing LncRNA HOXD-AS1 enhances the radiosensitivity of H460 cells by regulating miR-454-3p expression

Objective To explore the effect of LncRNA HOXD-AS1 on the radiosensitivity of H460 cells by targeting the regulation of miR-454-3p expression. Methods H460 cells were irradiated with 0, 2, 4, 6 and 8 Gy, and the expression levels of HOXD-AS1 and miR-454-3p were detected by qRT-PCR. Cell apoptosis rate were measured by flow cytometry experiments. Cell cloning experiments were used to detect cell radiosensitivity. The protein expression levels of Caspase-3, Cyclin D1 and γ-H2AX were detected by Western blot. Results The expression of HOXD-AS1 in H460 cells was significantly increased after X-ray irradiation (P<0.05), while the expression of miR-454-3p was significantly decreased (P<0.05). Silencing HOXD-AS1 significantly promoted apoptosis, increased radiosensitivity of lung cancer cells, promoted Caspase-3, γ-H2AX protein expression, and inhibited Cyclin D1 expression. HOXD-AS1 could target the expression of miR-454-3p. Conclusion Silencing HOXD-AS1 can promote the apoptosis of lung cancer cells and inhibit cell survival by targeting miR-454-3p to increase the radiosensitivity of lung cancer cells. Key words: LncRNA HOXD-AS1 gene; miR-454-3p gene; Lung cancer cell line; Radiosensitivity

Radio-selective effects of a natural occurring muscle-derived dipeptide in A549 and normal cell lines

Radiotherapy (RT) causes morbidity and long-term side effects. A challenge in RT is to maximize cancer cells killing while minimizing damage to normal tissue. The ideal radio-protector selectively improves survival and limits damage to normal tissues while reducing survival of cancer cells. Muscle-derived dipeptide, L-carnosine (CAR) is a potent antioxidant, with radio-protective, but also anticancer properties, affecting the cell cycle of cancer cells. We tested CAR effects in lung cancer cells, differentiated and undifferentiated normal cells. We hypothesized that CAR antioxidant properties will confer protection to the two normal cell lines against RT, while preventing lung cancer cell proliferation, and that CAR may act as a radiosensitizer of lung cancer cells due to its effects on cell-cycle progression of cancer cells. Under the experimental conditions reported here, we found that CAR increased radio-sensitivity of lung (A549) cancer cells by increasing the percentage of cells in G2/M (radiosensitive) phase of cell cycle, it negatively affected their bioenergetics, therefore reduced their viability, and DNA-double strand break repair capacity. CAR had either no effect or reduced RT-induced damage in normal cells, depending on the cell type. CAR is a versatile natural occurring compound, that could improve RT-induced lung cancer cells killing, while reducing the damage to normal differentiated and undifferentiated cells.

The influence of kinesin light chain-2 on the radiosensitivity of non-small cell lung cancer cells and the underlying mechanisms.

e14512 Background: Our previous study found upregulated kinesin light chain-2 (KLC2) in non-small cell lung cancer (NSCLC) cell lines and tissues, which is associated with a poor prognosis. KLC2 promotes the migration ability of lung cancer cells. However, the influence of KLC2 on radiosensitivity of NSCLC has not yet been reported. Methods: Sensitivity of lung cancer cells to radiation was analyzed by colony formation, γH2AX immunofluorescent staining assay and neutral comet assay in vitro and a xenograft tumor model in vivo. Gene set enrichment analysis (GSEA), qRT-PCR and western blot assay were performed to predict and validate the potential target genes of KLC2. Results: We found that down-regulation of KLC2 could significantly improve the radio-sensitivity of lung cancer cells, while the overexpression of KLC2 had the opposite effect. GSEA identified p53 signal pathway as differentially enriched with high KLC2 expression, which was validated by western blot assay. Using data from TCGA, we found a positive correlation between the mRNA level of KLC2 and that of HuR. The expression of KLC2 mRNA and protein in lung cancer cells was significantly reduced when downregulating HuR. Interestingly, the overexpression of KLC2 could also significantly decrease the expression of HuR. Conclusions: The above results indicated that HuR could upregulate the expression of KLC2, which might decrease the phosphorylation of p53 and thereby weakened the radio-sensitivity of NSCLC cells. KLC2 could also positively regulate the expression of HuR as a positive feedback. Support: 81572279, 2016J004, LC2016PY016, 2018CR033

Tissue-specific and exosomal miRNAs in lung cancer radiotherapy: from regulatory mechanisms to clinical implications.

Lung cancer is the most prevalent and deadly malignancy. Radiotherapy is a major treatment modality for lung cancer. Nevertheless, radioresistance poses a daunting challenge that largely limits the efficacy of radiotherapy. There is a pressing need for deciphering molecular mechanisms underlying radioresistance and elucidating novel therapeutic targets for individualized radiotherapy. MicroRNAs are categorized as small noncoding RNAs that modulate target-gene expression posttranscriptionally and are implicated in carcinogenesis and cancer resistance to treatment. Overwhelming evidence has unraveled that tissue-specific miRNAs are essential for regulation of the radiosensitivity in lung cancer cells through a complex interaction with multiple biological processes and radiation-induced pathways. Moreover, exosome-derived miRNAs are a novel horizon in lung cancer treatment in which exosomal miRNAs act as potential diagnostic and therapeutic biomarkers of radiotherapy. In the present review, we discuss the mediation of key biological processes and signaling pathways by tissue-specific miRNAs in lung cancer radiotherapy. Additionally, we provide new insight into the potential significance of exosomal miRNAs in radiation response. Lastly, we highlight miRNAs as promising predictors and therapeutic targets to tailor personalized lung cancer radiotherapy.

Extracellular signal-regulated kinase 5 increases radioresistance of lung cancer cells by enhancing the DNA damage response

Radiotherapy is a frequent mode of cancer treatment, although the development of radioresistance limits its effectiveness. Extensive investigations indicate the diversity of the mechanisms underlying radioresistance. Here, we aimed to explore the effects of extracellular signal-regulated kinase 5 (ERK5) on lung cancer radioresistance and the associated mechanisms. Our data showed that ERK5 is activated during solid lung cancer development, and ectopic expression of ERK5 promoted cell proliferation and G2/M cell cycle transition. In addition, we found that ERK5 is a potential regulator of radiosensitivity in lung cancer cells. Mechanistic investigations revealed that ERK5 could trigger IR-induced activation of Chk1, which has been implicated in DNA repair and cell cycle arrest in response to DNA double-strand breaks (DSBs). Subsequently, ERK5 knockdown or pharmacological inhibition selectively inhibited colony formation of lung cancer cells and enhanced IR-induced G2/M arrest and apoptosis. In vivo, ERK5 knockdown strongly radiosensitized A549 and LLC tumor xenografts to inhibition, with a higher apoptotic response and reduced tumor neovascularization. Taken together, our data indicate that ERK5 is a novel potential target for the treatment of lung cancer, and its expression might be used as a biomarker to predict radiosensitivity in NSCLC patients.